The first of two storms predicted this week brought some snow to the mountains and mostly modest amounts of rain as it moved through California on Monday, but some authorities were cautious about the potential for mudslides and debris flows. The storm descended through the San Francisco Bay Area in the morning and dropped snow in the Sierra Nevada, where travel was hobbled on Interstate 80 and U.S. 50. The relatively narrow storm band continued southward along the coast and also brought rain to the state’s Central Valley agricultural heartland.